How much does an iphone 4 cost without contract simple mobile?

As far as I can tell from their website, you have to buy the phones at full price.
http://www.mysimplephones.com/Simple-Mobile-iPhone/
But I would call and ask if I were you.

Massalinie M26.11.2012

$450.00 for an 8gb or buy one off a friend or ebay but if you want to put a service plan on it then id recamend unlocking it with green pois0n.

Liam26.11.2012

Like the other folks have said too, you have to pay full retail price which is pretty hefty. You could try eBay or Craigslist if you wanted, but you never really know where those phones are coming from.